Nucleic acid-labeled tags associated with odorant

ABSTRACT

A nucleic acid tag comprising a nucleotide-support platform attached to a nucleic acid molecule, an odorant, and an encapsulant. Unique nucleic acid-containing tags containing an odorant are seeded at one or more geographic locations. Using odorant-detection systems, the person or object of interest is examined for the presence of one or more of the odorant, thereby revealing the presence of the seeded nucleic acids and eliminating the expense and time associated with unnecessary screening. The geographic location associated with each detected nucleic acid is used to backtrack the item&#39;s path or extrapolate a probable point of origin.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/247,479, filed on Apr. 8, 2014 and entitled “Nucleic Acid-LabeledTags Associated with Odorant (now U.S. Pat. No. 9,315,852, to issue onApr. 19, 2016), which is a divisional of U.S. patent application Ser.No. 12/849,546, filed on Aug. 3, 2010 and entitled “Nucleic Acid-LabeledTags Associated with Odorant (now U.S. Pat. No. 8,716,027, issued on May6, 2014), the entireties of which are hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to nucleic acid-labeled tags, and, moreparticularly, to the use of an odorant as a screening element for thedetection of odorant-labeled nucleic acid-labeled tags.

2. Description of the Related Art

The physical characteristics of a nucleic acid molecule make it uniquelysuitable for use as a secure information-storage unit. In addition tobeing odorless and invisible to the naked eye, a nucleic acid moleculecan store vast amounts of information. It has been estimated that asingle gram of deoxyribonucleic acid (“DNA”) can store as muchinformation as approximately one trillion compact discs (“Computing WithDNA” by L. M. Adleman, Scientific American, August 1998, pg 34-41).

Nucleic acid molecules are also resilient to decay, even in vitro.Although a nucleic acid molecule typically begins to breakdown whenexposed to chemicals, radiation, or enzymes, some nucleic acid moleculescan survive for thousands of years. For example, scientists havesequenced the Neanderthal genome using DNA molecules that were recoveredfrom remains dating at least 38,000 years old.

Lastly, nucleic acid molecules are both ubiquitous in nature and largelyuncharacterized, with only a fraction of the world's organisms havingbeen sequenced. As a result of this uncharacterized environmentalbackground noise, inadvertent detection of a man-made nucleic acidmolecule is unlikely.

To employ the many beneficial characteristics of nucleic acids, thesemolecules can be incorporated into a secure tag. These tags can becomposed of deoxyribonucleotides, ribonucleotides, or similar moleculescomposed of nucleic acids that are either artificial (such as nucleotideanalogues) or are otherwise found in nature. The nucleic acids can rangefrom very short oligonucleotides to complete genomes.

Once a nucleic acid tag is created it can be used for numerous uniquesecurity applications including to: (i) detect illicit tampering withphysical objects; (ii) secure the privacy of a room or building; (iii)send encoded messages between individuals; (iv) detect a taggedindividual or object at a distance; (v) track the recent travel historyof an individual or object; or (vi) monitor a location of interest.

DNA tags have previously been used for other applications. For example,DNA tags have been removably attached to tangible assets to assist inthe identification of ownership in the event the asset is lost orstolen. Additionally, it has been proposed that DNA tags be used toprevent counterfeiting by incorporating tags into items during or afterproduction and using detection of such tags to authenticate the items.

SUMMARY OF THE INVENTION

It is therefore a principal object and advantage of the presentinvention to provide a nucleic acid tag that can be used in numeroussecurity-related applications.

It is a further object and advantage of the present invention to providea method of standoff detection using nucleic acid tags.

It is yet another object and advantage of the present invention toprovide a method of determining whether an object has traveled through alocation using seeded nucleic acid-labeled tags.

It is a further object and advantage of the present invention tobacktrack or identify an object's point of origin or recent geographiccourse using seeded nucleic acid-labeled tags.

It is yet another object and advantage of the present invention toprovide an odorant-associated nucleic acid-labeled tag.

It is a further object and advantage of the present invention to providea nucleic acid-labeled tag that with an odorant that co-locates with thetag.

It another object and advantage of the present invention to provide anucleic acid-labeled tag that with an odorant that, with its presence orabsence, indicates the presence or absence of the tag.

It is yet another object and advantage of the present invention toprovide a nucleic acid-labeled tag that with an odorant that cannot bediscerned by a human without the aid of an odorant detection device.

It is a further object and advantage of the present invention to providea nucleic acid-labeled tag that with an odorant that is covert,non-toxic, and which does not inhibit PCR analysis.

It is another object and advantage of the present invention to provide anucleic acid-labeled tag that with an odorant that cannot be detectedwith odor detection equipment unless the equipment has been trained toidentify the odorant in an operational setting.

Other objects and advantages of the present invention will in part beobvious, and in part appear hereinafter.

In accordance with the foregoing objects and advantages, the presentinvention provides a nucleic acid tag, the tag comprising: anucleotide-support platform attached to a nucleic acid molecule; and anodorant. According to one embodiment, the odorant is a syntheticchemical, although it can be any chemical known to be capable ofdetection with or without the aid of an odorant detection device.

Another embodiment of the present invention provides for a nucleic acidtag, the tag comprising: a nucleotide-support platform attached to anucleic acid molecule; an odorant; and an encapsulant, where theencapsulant is adapted to prevent degradation of the nucleic acidmolecule.

A further embodiment of the present invention provides a method ofdetermine whether an item has moved through a geographic location, themethod comprising: seeding a geographic location with a nucleic acid tagcomprised of a nucleotide-support platform attached to a nucleic acidmolecule, and further comprising an odorant; and screening the item forthe presence or absence of the nucleic acid tag.

Another embodiment of the present invention provides a method ofdetermine whether an item has moved through a geographic location, themethod comprising: seeding a geographic location with a nucleic acid tagcomprised of a nucleotide-support platform attached to a nucleic acidmolecule, and further comprising an odorant; and screening the item forthe presence or absence of the nucleic acid tag, where the step ofscreening comprises the steps of screening the item for the presence ofthe odorant, and if the odorant is present, characterizing the nucleicacid tag.

Yet another embodiment of the present invention is a method forbacktracking the travel history of an item, the method comprising:seeding a first geographic location with a first nucleic acid, the firstnucleic acid tag comprising a first nucleotide-support platform attachedto at least a first nucleic acid molecule and further comprising anodorant; seeding a second geographic location with a second nucleicacid, where the second nucleic acid tag comprises a secondnucleotide-support platform attached to at least a second nucleic acidmolecule and further comprising an odorant; screening the item for thepresence or absence of one or more nucleic acid tags; and identifyingthe geographic location associated with each nucleic acid tag detectedon the item.

A further embodiment of the present invention is a method forbacktracking the travel history of an item, the method comprising:seeding a first geographic location with a first nucleic acid, the firstnucleic acid tag comprising a first nucleotide-support platform attachedto at least a first nucleic acid molecule and further comprising anodorant; seeding a second geographic location with a second nucleicacid, where the second nucleic acid tag comprises a secondnucleotide-support platform attached to at least a second nucleic acidmolecule and further comprising an odorant; screening the item for thepresence or absence of one or more nucleic acid tags, where the step ofscreening further comprises the steps of screening the item for thepresence of the odorant, and if the odorant is present, characterizingthe one or more nucleic acid tags; and identifying the geographiclocation associated with each nucleic acid tag detected on the item.

Another embodiment of the present invention is a method for determiningthe point of origin of an item, the method comprising: seeding each oftwo or more geographic locations with a unique nucleic acid tag, the tagcomprising a nucleotide-support platform attached to at least onenucleic acid molecule, and further comprising an odorant; screening theitem for the presence or absence of one or more nucleic acid tags;identifying the geographic location associated with each nucleic acidtag detected on the item; and extrapolating the point of origin.

Yet another embodiment of the present invention is a method fordetermining the point of origin of an item, the method comprising:seeding each of two or more geographic locations with a unique nucleicacid tag, the tag comprising a nucleotide-support platform attached toat least one nucleic acid molecule, and further comprising an odorant;screening the item for the presence or absence of one or more nucleicacid tags, where the step of screening further comprises the steps ofscreening the item for the presence of the odorant, and if the odorantis present, characterizing the one or more nucleic acid tags;identifying the geographic location associated with each nucleic acidtag detected on the item; and extrapolating the point of origin.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated byreading the following Detailed Description of the Invention inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic representation of nucleic acid tag production.

FIG. 2 is a schematic representation of an embodiment of the methodaccording to the present invention.

FIG. 3 is a side view of an encapsulated nucleotide tag complex.

FIG. 4 is a side view of encapsulated nucleotide-derivatizednanoparticles.

FIG. 5 is a side view of an encapsulated tag complex containing aretroreflector and nucleotide-derivatized nanoparticles.

FIG. 6 is a side view of an encapsulated nucleotide tag complex withodorant trapped inside the tag by the encapsulant layer.

FIG. 7 is a side view of an encapsulated nucleotide tag complex withodorant incorporated into the encapsulant layer.

FIG. 8 is a side view of an encapsulated nucleotide tag complex withodorant coating the outer surface of the encapsulant.

FIG. 9 is a side view of an encapsulated nucleotide tag complex withodorant coating the inner surface of the encapsulant.

FIG. 10 is a side view of an encapsulated nucleotide tag complex withodorant incorporated into the nanoparticles.

FIG. 11 is a side view of an encapsulated nucleotide tag complex withseparate marker elements.

FIG. 12 is a side view of an encapsulated nucleotide tag complex withmarker elements coating the outer surface of the encapsulant.

FIG. 13 is a side view of an encapsulated nucleotide tag complex withmarker elements incorporated into the encapsulant layer.

FIG. 14 is a side view of an encapsulated nucleotide tag complex withmarker elements incorporated into the nanoparticles.

FIG. 15 is a side view of an encapsulated nucleotide tag complex withmarker elements trapped inside the tag by the encapsulant layer.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like reference numerals designateidentical or corresponding parts throughout the several views, there isshown in FIG. 1 a schematic representation of nucleic acid tagproduction. As an initial step 10, a nanometer-sized particle(“nanoparticle”) platform is prepared for attachment to the nucleic acidmolecule(s). A platform is used to make the nucleic acid more accessibleto downstream analysis and prevent nucleic acid loss if any portion ofthe encapsulating layer is compromised.

The platform is any compound that can be attached to nucleic acidwithout unintentionally degrading or altering the nucleic acid sequence.For example, the platform can be a lightweight, durable, non-watersoluble, and chemically inert structure composed of silica orpolystyrene. Additionally, the nanoparticle platform should be composedof a compound that does not inhibit any downstream analysis of thenucleic acid molecules, including tag detection and polymerase chainreaction (PCR).

In step 12, the nucleic acid molecule is attached to the preparednanoparticle platform. The nucleic acid molecules are optimally attachedto the nanoparticle to facilitate later analysis. In a preferredembodiment, a chemical linker is used to connect the nucleic acid to thenanoparticle platform. This chemical linker must keep the nucleic acidsecurely tethered to the nanoparticle while avoiding inhibition of thedetection or analysis of the tag and nucleic acid. Although the chemicallinker can be chosen to provide a permanent covalent link between thenucleic acid and the nanoparticle platform, it could also be a compoundthat quickly and efficiently releases the nucleic acid at a certaintemperature or after exposure to a release compound. In one embodiment,the chemical linker is the odorant, or also links to the odorant. Thisembodiment guarantees co-localization of the odorant and the nucleicacid-labeled tag, potentially provides stability to the odorant, andpotentially provides for efficient downstream analysis of the associatednucleic acid.

The nucleic acid molecule can also be designed to promote analysis. Forexample, to avoid steric hindrance or unwanted intermolecularinteractions, the molecule can include nucleotide spacers between thechemical linker or nanoparticle base and the information-coding segmentof the nucleotide sequence. Spacing between 5 and 15 bases has beenoptimal for current applications, although this may vary as newapplications are considered.

The concentration of nucleic acid molecules on the nanoparticle platformis also an important factor in downstream analysis. If the molecules aretoo concentrated, steric hindrance prevents the primer and polymerasefrom efficiently binding the proper segments of the nucleic acidmolecules. If the molecules are too sparse, the PCR signal will bediminished and can result in false negatives. In the preferredembodiment, a concentration of about 3×1010 nucleic acid molecules persquare centimeter is the optimal concentration for robust PCR signal.

In step 14, the nucleic acid-derivatized nanoparticles are agglomerated.Agglomeration protects the nucleic acid molecules from degradation andfacilitates encapsulation. To agglomerate the particles to the desiredsize range, the nanoparticles are vacuum dried, milled, and sieved.

Compounds might be used or incorporated into the tag to promotedisagglomeration of the agglomerates prior to PCR analysis. Thesecompounds might be bovine serum albumin, salmon sperm DNA,carbohydrates, polyvinyl alcohol, fructose, or chitosan, among others.With more nucleic acid exposed during dissolution, subsequent analysiswill be faster and more sensitive.

After the nanoparticles are agglomerated, the agglomerates can beencapsulated in step 16. The encapsulant protects the nucleic acid fromdegradation by ultraviolet light, hydrolysis, enzymatic digestions,chemical degradation, or any other means. Additionally, the encapsulantcan be designed such that it does not hinder analysis of the nucleicacid molecules. For example, the encapsulant should not contain anycompounds that would inhibit or prevent a PCR reaction, althoughefficient removal of the encapsulant before PCR analysis would eliminatethis requirement. Additionally, the encapsulant should enhance theability of the tag to discretely attach to people and objects. Ifcovertness is required, the encapsulant can be designed to deterdetection.

The encapsulating layer can also be designed with surface moieties addedto the inner or outer surfaces of the encapsulant or incorporated intothe encapsulant material. The moieties are designed to facilitate aparticular use of the nucleic acid tag. For example, the moiety can behydrophobic to enable stickiness or contain antibodies designed forspecific targeting. The molecular interactions between the moiety and atarget compound can range from simple electrostatic interactions toantibody-antigen recognition. The moiety can also promote detection ofthe nucleic acid tag. In one embodiment, the encapsulating layer iscomposed of or comprises an odorant that promotes detection of the tag,as discussed in detail below.

To protect the nucleic acid from degradation, the encapsulating layercan be coated with or include another functional layer of material. Forexample, the encapsulant can be coated with or include anon-water-soluble compound to prevent access to water or similarmolecules. The encapsulant can also be coated with or include aUV-blocking compound such as titanium dioxide to prevent UV-induceddegradation of the nucleic acid molecules.

The tag can also include an odorant, as shown in step 17 of FIG. 1. Theodorant is preferably anything known to be capable of detection bymechanical means or by human or animal means (i.e., olfactiondetection). The odorant can comprise anything known by those skilled inthe art to be capable of detection, including a single aromatic, a blendof aromatics, or a commercially available synthetic chemical, among manyothers. Since the surfaces on which the odorant might be detected willvary, the odorant will preferably be unique or distinctive enough to bedetected over random odorants present on these surfaces or in thesurrounding environment. Although according to one embodiment theodorant is capable of detection by humans and/or animals, in thepreferred embodiment the odorant can only be detected by animals and/orelectronic means, thereby evading human detection. For example,mechanical means such as an “electronic nose” could be programmed ortrained to recognize the odorant and alert the user to its presence. Ina preferred embodiment, the sensor provides quantitative informationabout detection and is sensitive enough to detect very minute or traceamounts of the odorant.

FIG. 2 is a schematic representation of an embodiment of a securitymethod according to the present invention. More specifically, the figurerepresents characterization of the recent travel history of point of anitem. An item can be any person or object of interest. Seeding an areawith tags that naturally or artificially adhere to objects (includingpeople or animals) provides a mechanism for identifying the origin ofthose objects simply by analyzing the adhering tags. Similarly, byseeding different areas with discernibly different tags it is possibleto backtrack the geographic path that an object has followed. Such amechanism would allow the seeder—the person or organization who seededand will analyze the tags—to identify the recent travel history of theperson or object; to quickly identify people or objects that havetraveled through seeded areas; and to identify vehicles that havetraveled through seeded areas and might carry dangerous cargo such asexplosives, among other uses.

As an initial step 18, an identifiable nucleic acid is characterized orcreated. In one embodiment of the present invention, the sequence rangesfrom a short oligonucleotide to an entire genome and is generatedthrough any of the various known methods of natural or artificialnucleic acid synthesis. The nucleic acid can be completely composed ofeither natural nucleic acids which normally compose the genomes oforganisms, artificial nucleic acids, or a mixture of the two.

In the preferred embodiment of the tag, the nucleic acid molecules ofeach type of tag—which typically differ depending on location or mannerof use—contain identical primer-binding sequences surrounding uniquenucleotide sequences. Each unique nucleotide sequence contained betweenthe primers encodes information that corresponds to the location, time,or other data specific to that unique sequence. Since analysis of adetected tag uses the same primers, the analysis is performed faster andmore efficiently.

The primer sequences, whether they are unique or identical for eachlocation or use, are chosen to avoid cross-reactions withnaturally-occurring nucleic acid molecules in the environment in whichthe tag is located. Although only a fraction of natural nucleic acidmolecules on Earth have been characterized by scientists, the search ofnucleic acid repository databases such as GenBank®, the NationalInstitutes of Health database containing all publicly available DNAsequences, should be a preliminary step in constructing the primersequences.

In one embodiment of the current invention, unique groupings ofnucleotides are assigned a specific letter, number, or symbol value inorder to encode information within the sequence. By placing the uniquegroupings in order, information can be encrypted into the nucleotidesequence. To further increase the security of the information, advancedencryption algorithms can be used to assign letter, number, or symbolvalues to specific nucleotides or nucleotide groupings. Additionally,the encryption system can be periodically changed to prevent decryptionby intercepting entities.

The nucleic acid can also be encoded to contain information other than astring of letters, numbers, and symbols. For instance, the sequence canbe a random sequence that corresponds to the latitude and longitude ofthe site that will be seeded. Alternatively, the tag can be as simple asa single nucleic acid change in a previously identified or knownsequence. For example, the nucleotide sequence can be embedded in a fullor partial genomic sequence corresponding to an organism which naturallyexists in the location to be seeded. Modifications to the naturalnucleic acid sequence, known only to the creator of the tag, can be madesuch that the changes resemble natural variations of the sequence andthus fail to arouse suspicion, even by individuals that might suspectsuch tags are present.

To decrypt the encoded information according to this system, anindividual will need: (1) knowledge that encoded nucleic acid ispresent; (2) knowledge of the specific location of the informationwithin the nucleic acid in order to use the appropriate primers foramplification and sequencing reactions; (3) access to a PCR machine andreagents; and (4) the encryption algorithm, or, alternatively, complexdecryption capabilities.

Although creating the tag within the genome of an naturally-occurringorganism provides numerous benefits, both in vivo and in vitro DNAreplication occasionally introduces random errors into a DNA sequencedespite the actions of proof-reading and repair enzymes. By deleting oneor more nucleotides or frame-shifting the nucleic acid sequence, thesemutations can disrupt any encrypted information contained therein.Computer algorithms are used to restore the information by recognizingand repairing the errors. For example, if a mutation adds one or morenucleotides to a pre-defined sequence and disrupts the information, thealgorithm removes single or multiple nucleotides from the sequence untilthe information is corrected. Similarly, if a mutation removes one ormore nucleotides, the algorithm systematically adds nucleotides to thesequence until the information is corrected. The algorithm must also berobust enough to decrypt sequences that contain more than one type oferror-inducing mutation, and must be capable of recognizing when theinformation contained with the nucleic acid has been restored.

In step 20 of FIG. 1, the nucleic acid is packaged into an appropriatetag complex. To avoid potentially harmful environmental side-effects,the tag can be large enough to avoid being inhaled by people ororganisms but small enough to be covert. FIG. 3 represents oneembodiment of this tag structure. Tag 30 is composed of a singlenucleotide-support platform 32, nucleic acid 34, and encapsulant 36.

FIG. 4 is a side view of another embodiment of the tag structure. Tag 38is composed of nucleotide-support platform 40 derivatized with nucleicacid 42 and surrounded by encapsulant 44. Similar to the tag in FIG. 3,tag 38 contains nucleic acids that are contained within an encapsulantthat protects the sequence without inhibiting later analysis. Unlike thebead platform used by the tag in FIG. 3, nucleotide-support platform 40is composed of nanoparticles. Tag 38 can contain thousands, millions, oreven billions of nucleotide-derivatized nanoparticles within theencapsulant layer. In several of the described embodiments, theencapsulant layer must be designed to prevent inhibition of excitationand emission wavelengths.

FIG. 5 is yet another embodiment of the tag complex. Encapsulated tag 46contains a retroreflector 48, nucleotide-derivatized nanoparticles 50,and encapsulant 52. Retroreflector 48, a device that reflects anelectromagnetic wave front back along a vector that is parallel to butopposite in direction from the angle of incidence, forms the center oftag 46. The retroreflector must be situated to allow electromagneticwaves to hit and reflect from the surface. To prevent obstruction of theretroreflector, the tag is organized to keep nucleotide-derivatizednanoparticles 50 away from the surface of the retroreflector, as shownin FIG. 5. Additionally, encapsulant 52 must protect the tag complexwithout interfering with the retroreflector's reflectivity. As analternative to the nanoparticle format shown in FIG. 5, the nucleic acidcan coat the non-reflective surfaces of retroreflector 48. In anotherembodiment of the retroreflector tag, the non-reflective surfaces of theretroreflector are coated with nucleic acid and only those surfaces arecovered by a protective encapsulant.

In yet another embodiment, the tag complex can include an odorant 56that provides a preliminary level of screening. By quickly andaffordably pre-screening for the presence of the odorant, the screenercan determine whether the tag might be present without performing swabsor extensive downstream DNA analysis, thereby lowering the time and costassociated with screening.

The odorant 56 can be incorporated into the tag in a number of differentways. For example, in FIG. 6 the odorant is separate fromnucleotide-support platform 40 and encapsulant 44 but is trapped withinthe interior of tag 38. In this configuration, the encapsulant must beconstructed such that the odorant is capable of detection. In FIG. 7,odorant 56 is incorporated into encapsulant 44. In FIG. 8, the odorantforms a layer on the exterior surface of the encapsulant. Odorant 56could also coat the interior surface of the encapsulant, as shown inFIG. 9. In FIG. 10, the odorant coats the surface of nucleotide-supportplatform 40.

In step 22 of FIG. 2, one or more geographic locations are seeded withthe tags. The locations are seeded with tags using any mechanism thatwill adequately disperse the tags at the desired concentration. Forexample, the tags can be seeded on and along roadways or paths using anautomobile that has been modified to disperse the tags. The tags canalso be discretely dispersed from the air using an airplane orremotely-controlled flying apparatus. Tags can even be seeded byindividuals using hand-held dispersal systems.

To efficiently backtrack the movements of a person, vehicle, or object,each road within a given location can be seeded with a unique tag. Asthe vehicle moves through the location it picks up tags from each roadit traverses. This system can be scaled up or scaled down to suit theneeds of the seeder. For example, rather than seeding individual roadsthe seeder can use the tags to label large regions of land to backtracklarge-scale movements. Alternatively, the seeder can scale down themethod by seeding individual homes or buildings to identify individualsor objects that have entered those buildings.

In step 24 of FIG. 2, an item is examined for the presence of seededtags. Once an object of interest is identified, the object can beexamined for seeded tags using any mechanism designed to pick up tagsfrom the surfaces of the object. For example, the tires, wheel wells, orunderside of a vehicle can be swabbed for tags. If the object ofinterest is a person, the individual's clothes, shoes, hair, or skin canbe swabbed for tags. If the object of interest is a post-blast fragmentof an explosive device, the surfaces of the fragment can be swabbed forany tags that survived the explosion.

If the seeded tags contain an odorant, odorant-detection means such ashuman or animal olfaction detection or electronic sensordetection—including a chemical sensor, an electronic nose, MEMS sensor,or any other type of odorant-detection or chemical-detection sensorknown to those skilled in the art—can be used to detect the presence oftags. Detection of the seeded tag by olfaction or an odorant sensorprovides a number of useful advantages. For example, this screening stepreduces the number of samples that must be analyzed by downstream DNAtechniques. Without screening, samples must be blindly recovered fromevery surface and analyzed for detection of the nucleic acids. With theodorant, samples are only recovered from surfaces that likelyencountered the odorant and thus the nucleic acid-labeled tag. Further,pre-screening for the odorant limits the area needed for sampling byconcentrating the samples to only the areas where the odorant isdetected. Alternatively, the odorant can limit the amount of worknecessary to screen samples that have already been gathered. Forexample, if 1,000 different samples are taken from one or more surfaces,only those samples that are shown to contain odorant will be analyzedfurther.

In another embodiment multiple odorants could be seeded with the tags,and pre-screening would rule out the need to PCR-analyze samples forsuites of tags. This embodiment would require odorants which would notinterfere with the detection of other odorants, such that individualodorants could be resolved from a mixture of odorants. Multiple sensorscould be employed in this embodiment.

If the seeded tags contain retroreflectors, electromagnetic waves can beused to detect the presence of tags. Scanning equipment shines light onthe object of interest and looks for a wave front that is reflectedalong a vector that is parallel to but opposite in direction from thewave's source. This suggests that retroreflective tags are present onthe surface of the object and alerts the authorities that furtherinvestigation is necessary. This rapid and cost-effective identificationof retroreflective tags is especially useful for high-throughputlocations such as checkpoints and border crossings. Once theretroreflective tags are detected, they can be removed from the surfacesof the object for analysis of the attached nucleic acids to identifygeographic locations.

The tags can also contain luminescent compounds that reveal theirpresence from a distance. Although the preferred embodiment usesfluorescent or phosphorescent photoluminescence, other embodiments mayinclude chemiluminesent, radioluminescent, or thermoluminescentcompounds. The photoluminescent compound is chosen such that absorptionof a photon with a certain wavelength by the compound causes theemission of a photon with a different wavelength. The difference betweenthe wavelength of the absorbed photon and the wavelength of the emittedphoton depends on the inherent physical properties of the chosencompound.

In the preferred embodiment, the luminescent compound absorbs and emitsphotons in the ultraviolet band—between 10 and 400 nanometers—of theelectromagnetic spectrum. The compound is chosen to avoid interferenceby UV radiation from the sun. The Earth's atmosphere absorbs as much as99% of the UV radiation emitted by the sun in the 150-320 nm range. Thusthe most advantageous luminescent compound absorbs and emits photonswith wavelengths below 320 nm.

As an alternative to luminescent compounds that absorb and emit photonsin the 150-320 nm range, compounds that absorb and emit photons ofwavelengths greater than 320 nm can be used under certain circumstances.For example, these compounds could be used during nighttime conditionsor in an enclosed UV-blocking environment such as a windowlessstructure.

The luminescent compound can be incorporated into the tag in a number ofdifferent ways. For example, in FIG. 11 the compound 54 is entirelyseparate from tag 38. In FIG. 12, compound 54 forms a layer on theexterior surface of encapsulant 44. The compound could also coat theinterior surface of encapsulant 44. In FIG. 13, compound 54 isincorporated into encapsulant 44. In FIG. 14, compound 54 coats thesurface of nucleotide-support platform 40. In FIG. 15, compound 54 isseparate from nucleotide-support platform 40 and encapsulant 44 but istrapped within the interior of tag 38. In several of the describedembodiments, the encapsulant layer must be designed to preventinhibition of excitation and emission wavelengths.

If the seeded tags contain a photoluminescent compound, electromagneticwaves can be used to detect the presence of tags at a distance. Scanningequipment shines photons of the excitatory wavelength on the object ofinterest and looks for photons emitted at the proper wavelength asdetermined by the compound used in the tags. Detection of photons withthe correct wavelength suggests that a nucleic acid-labeled tag ispresent and alerts the scanner that further investigation is necessary.The advantage of this system is that the scanning equipment and tag canbe designed such that the individual doing the scanning does not have tobe in close proximity to the object of interest.

The detection process can also be automated. An individual or object ofinterest can be forced to travel through a scanning point containingexcitation equipment and emission detection equipment. As the individualor object of interest travels through the scanning point, the equipmentscans for emitted photons of a certain wavelength. When the emittedphotons are detected, a computer at the scanning point automaticallyalerts a remotely-located entity that subsequent analysis is necessary.

In yet another embodiment of the current invention, the nucleic acidscontained within the tags taken from the surface of an object areanalyzed using any method that determines the exact order of nucleotidebases. There are currently a number of different commonly-usedsequencing techniques including but not limited to dye-terminatorsequencing, parallel sequencing, and sequencing by ligation. Sequencingmachines allow automated sequencing and can be run 24 hours a day. IfPCR techniques are used, the appropriate primers are chosen based uponthe types of tags known to be in the location of interest. Prior tosequencing or amplification, it is necessary to dissolve or otherwiseremove the encapsulant layer from the tag in a manner that avoidsinhibition of the downstream sequencing or PCR reactions. In thepreferred embodiment, the encapsulant and/or agglomerate is disrupted bybead beater, a form of mechanical disruption. This one-step methodavoids chemicals or extractions which could affect or inhibit PCRreactions.

In addition to the traditional sequencing techniques described above,real-time PCR and sequencing by hybridization techniques allow rapiddetection of target nucleic acids. According to the real-time PCRtechnique, the extracted nucleic acid is placed into a well or tube thathas been pre-loaded with all reagents necessary for a PCR reaction aswell as a sequence-specific, nucleotide-based, fluorescently-labeledprobe. As the extracted nucleic acid is amplified, the polymerasedegrades the probe and releases the fluorescent reporter. The reporterimmediately fluoresces and alerts the system to the presence of a tagnucleotide. Under the sequencing by hybridization technique, theextracted nucleic acid is labeled with a fluorescent marker and ishybridized to a DNA microarray that contains the complementarynucleotide sequence from known seeded tags. If the extracted nucleicacid hybridizes to any of the complementary tags, the fluorescent signalalerts the system to the presence of a target nucleic acid.

In step 26 of FIG. 2, the sequences obtained from the identified tagsare compared to a database of sequences attached to seeded tags. Toefficiently determine the point of origin or recent travel history of anobject, the individuals analyzing tags detected in the field will needaccess or information about the tags dispersed by the seeder. A databaseof seeded tags will require maximum security measures to avoid improperaccess and manipulation, including access protection measures such aspasswords. Standard computer algorithms are used to find exact orapproximate matches between a sequence in the field and a tag sequencein the database. Once such a match is found, the user can reasonablysuspect that the object of interest has recently traveled through thelocation seeded by that tag. If the real-time PCR or sequencing byhybridization techniques are used, the identification of the seeded tagsis quickly determined by equipment that scans the plate or microarrayfor fluorescent label.

Step 28 of FIG. 2 is an optional step which is only required if the useris attempting to backtrack the route taken by an object of interest orextrapolate the object's point of origin. According to some uses of thepresent invention, simply learning that a person or object has traveledthrough a particular location is sufficient information. For other uses,it is necessary to analyze the sequences of multiple tags. Toextrapolate a route taken or a point of origin, the seeded tag locationinformation obtained by analyzing the surfaces of the object is fed intoa computer algorithm that quickly plots every potential route that theobject has traveled based upon the possible combinations of taglocations. A similar algorithm can be used to extrapolate a point oforigin based upon the identified tag locations.

Although the present invention has been described in connection with apreferred embodiment, it should be understood that modifications,alterations, and additions can be made to the invention withoutdeparting from the scope of the invention as defined by the claims.

What is claimed is:
 1. A method for backtracking the travel history ofan item, the method comprising: seeding a first geographic location witha first nucleic acid tag, said first nucleic acid tag comprising anagglomerated plurality of nanoparticle nucleotide-support platforms eachattached to a plurality of nucleic acid molecules, and furthercomprising an encapsulant surrounding said agglomerated plurality ofnanoparticle nucleotide-support platforms and said plurality of nucleicacid molecules, wherein at least some of said nucleic acid moleculescomprise identifying information, and wherein said first nucleic acidfurther comprises a first odorant; seeding a second geographic locationwith a second nucleic acid tag, said second nucleic acid tag comprisinga plurality of nanoparticle nucleotide-support platforms each attachedto a plurality of nucleic acid molecules, and wherein said secondnucleic acid further comprises a second odorant, wherein said secondnucleic acid tag is different from said first nucleic acid tag;detecting one or more of the seeded nucleic acid tags on the item;identifying the respective geographic location associated with each ofthe one or more nucleic acid tags detected on said item; anddetermining, based on the identified geographic locations, a travelhistory of the item.
 2. The method of claim 1, wherein said secondnucleic acid tag comprises: an agglomerated plurality of nanoparticlenucleotide-support platforms, wherein at least some of said nucleic acidmolecules in said second nucleic acid tag comprise identifyinginformation; and an encapsulant surrounding said agglomerated pluralityof nanoparticle nucleotide-support platforms and said plurality ofnucleic acid molecules.
 3. The method of claim 1, wherein said firstodorant and said second odorant are the same odorant.
 4. The method ofclaim 1, further comprising the step of characterizing the odorantassociated with each of the one or more nucleic acid tags detected onsaid item.
 5. The method of claim 1, wherein said identifyinginformation is encrypted within the nucleic acid molecules by alteringthe sequence of nucleotides.
 6. The method of claim 2, wherein saididentifying information is encrypted within the nucleic acid moleculesby altering the sequence of nucleotides.
 7. The method of claim 1,wherein at least some of said first or second nucleic acid tags comprisea retroreflector.
 8. The method of claim 1, wherein said first or secondodorant is a synthetic chemical.
 9. The method of claim 1, wherein theencapsulant is adapted to prevent degradation of the plurality ofnucleic acid molecules.
 10. The method of claim 1, wherein each nucleicacid molecule is genomic deoxyribonucleic acid ranging from twonucleotides to the entire genome.
 11. The method of claim 1, whereininformation is encrypted within the genomic deoxyribonucleic acidmolecule by altering the sequence of nucleotides.
 12. The method ofclaim 1, wherein at least some of said first or second nucleic acid tagscomprises a luminescent compound.
 13. The method of claim 12, whereinsaid luminescent compound emits photons with a wavelength within therange of ultraviolet radiation.
 14. The method of claim 13, wherein thepresence of the nucleic acid tag is determined by exposing the item toelectromagnetic radiation.
 15. The method of claim 1, wherein the stepof screening said item for the presence of one or more nucleic acid tagscomprises the steps of: screening the item for the presence of saidodorant; and if said odorant is present, characterizing said one or morenucleic acid tags.
 16. A method for determining the point of origin ofan item according to claim 1, the method further comprising:extrapolating a point of origin for the item, wherein the point oforigin is a previous location of the item.